The advantages of computers are obvious and have been covered by the previous answers. I would like to discuss the disadvantages.
Computers have put millions of people out of work. For example, they have ravaged the book-selling business. Book stores are closing all across the country because it is so much more convenient to buy books online and so much easier to find the books you want. But in many cases it is possible to read books on the monitor or to print them. Computers have created jobs but not as many as they have displaced. They are only in their infancy, too. More and more shopping is being done online. Even the supermarkets are being affected. It looks as though the cities are going to be transformed in coming years, and many small towns are already being wiped out of existence.
Another disadvantage of personal computers is that they are addictive. Everywhere you go you see people staring into their laptops, and you may wonder, as I do, what they are thinking and what they find so hypnotic.